Wire antenna with moveable supports to change the shape



July 1, 1969 D. J. THOMPSON 3,453,630

WIRE ANTENNA WITH MOVEABLE SUPPORTS TO CHANGE THE SHAPE Filed Sept. 21.1966 Sheet Of 3 DOUGLAS 1/. 7Z/aMPsaM v BY/514,4

ATTORNEY y 1, 1959 D. J. THOMPSON 3,453,630

WIRE ANTENNA WITH MOVEABLE SUPPORTS TO CHANGE THE SHAPE Filed Sept. 21.1966 Sheet ,3 of5 N VE/V 7'0 DOUGLAS d. Dam/ 5M Swiz /M July 1, 1969 D.J. THOMPSON 3,

WIRE ANTENNA WITH MOVEABLE SUPI"ORTS TO CHANGE THE SHAPE I Filed Sept.21, 1966 Sheet 5 3" 3 FIG.5

Flag lNVEA/TOR DOUGLA s J. 7Z/oMPsoA/ sYl,/M

A Woe/w: v

United States Patent US. Cl. 343-757 9 Claims ABSTRACT OF THE DISCLOSUREAn antenna formed by directing an electrical conductor around severalsupport points. One or more of the supports is moveable to change theshape of the antenna.

This invention relates to UHF/VHF antennae, and more particularly toimprovements in antenna systems for increasing the quality of thesignals received thereby.

The development of antennae for UHF/VHF electromagnetic signal receptionhas included many innovations designed to increase the gain of theantenna (the amount of useful electrical energy derived through theantenna from a remotely-transmitted signal). A problem encountered inthe reception of signals from commercial television broadcastingstations is that the antenna used must be suitable to receive signalsfrom a plurality of transmitting stations of different frequencies, andthe antenna must operate at a minimum standard of performance relativeto all of the stations which may be received. In general, this problemhas been solved by developing antennae having broad-band frequencycharacteristics of various highly-sophisticated designs such that,although optimum performance is not achieved with respect to any onestation, acceptable performance is achieved with respect to all of them.

However, various interfering signals (such as other stations, noise andstatic) may not be adequately attenuated within a broad-band antennarelative to the strength of the signal received from the desiredtransmitting station. Therefore, an alternative solution to themulti-frequency requirements of receiver antennae has been to provide atunable antenna. Tunable antennae heretofore available in the radiofrequency bands have been comprised of telescopic elements, so as topermit extension and contraction of the receiving elements, and areexemplified by United States Patent No. 2,476,469 to Walker and UnitedStates Patent No. 2,599,048 to Dicke. At the lower radio frequencies,this design is useful, since the electrical length of the receivingelement is varied as the physical size is varied. However, at higherfrequencies, such as in the VHF and UHF television bands, the electricalproperties of telescoping antennae become more complex, and sucha designno longer achieves optimum tuning. A first reason for this is that theantenna elements continue to have the same mass at any length to whichthey are tuned. As the length is decreased, elemental units ofinductance tend to become elemental units of capacitance. The mass as awhole therefore tends to resonate at more nearly the same frequency,even though its physical length is changed. It follows that telescopingelements are less effective in achieving electrical tuning by changingphysical size in the VHF and UHF bands.

An undesired transmitting station which is located at a great distancefrom the receiving antenna may at times tend to interfere with a desiredtransmitting station having the same frequency. Furthermore, noise,static and other spurious signals may tend to emanate from varioussources within the effective range of the antenna. Rotating adirectional antenna provides significant attenuation of all signalswhich do not emanate from the direction in which the antenna is pointed.But it is also known in the prior art that any transmitted signalreceived at the receiving elements of an antenna over a slightly remotepath (such as being reflected thereto from a reflectory object) may havesuch a phase relationship with respect to another signal which arrivesat the antenna receiving elements over a direct path, that the signalsmay add to or subtract from one another. This is due in part to the factthat transmitting stations transmit a pattern which is generallynon-directional, therefore covering all points of the compass. It isalso due to the fact that, although the transmitted electromagneticradiation is generally horizontally polarized, the signals radiated fromthe transmitter are not all perfectly horizontal; thus some signals aredirected somewhat downwardly, at a lower angle than other signals. Theselow-angle signals (called ground waves) are reflected from the ground,upwardly, and may be received at the receiving elements of the antennaat a time which is somewhat later than the time that the directlyreceived, horizontally oriented signals are receivedv Similarly,radiation which is initially transmitted in a different direction may bereflected over a few degrees so that even though initially radiatedhorizontally, the horizontal distance to the receiver is longer than thecomparable distance for simultaneously transmitted electromagnetic waveswhich are directly received from the transmitting station. Where thedesired signals are of such a phase orientation as to be additive, theyprovide a relatively high-strength signal area, called space loops.Where they are subtractive, they provide a relatively lowstrength areacalled space nodes. The elimination of noise, interfering stations, andghosts may therefore be fully achieved by using a tunable antenna havingthe directional ability described heretofore, and capable of beingpositioned within the space loops rather than the space nodes.

It is an object of the present invention to provide an improvedmulti-frequency UHF/VHF receiving antenna assembly.

Another object is to provide such an improved antenna assembly having ahigh gain characteristic at a variety of different frequencies.

It is also an object to provide such an antenna assembly having a highratio of desired signal strength to noise and interfering transmitterstation signals.

Still another object is to provide such an antenna assembly which isrelatively economical and simple to manufacture and which is relativelysimple in operation so as to be adapted to use with home televisionreceivers.

A specific object is to provide a novel antenna assembly for receivingUHF/VHF signals which is capable of being properly oriented into aparticular point in space to take advantage of maximum desired signalstrength and capable of frequency adjustment without having unwantedconductor stubs and the attendant multiple signals which create ghostpatterns and signal losses.

Other objects and advantages will be readily apparent from the followingdetailed description and the accompanying drawings wherein:

FIGURE 1 is a fragmentary rear perspective view of an antenna assemblyembodying the present invention with a portion of the mast and mast stubbroken away to reveal internal construction;

FIGURE 2 is a schematic illustration of an embodiment of the form of abow tie antenna;

FIGURE 3 is a fragmentary front perspective view of an antenna assemblyembodying the bow-tie design of FIGURE 2;

FIGURE 4 is a fragmentary rear view of another antenna assemblyembodying the present invention;

FIGURE 5 is a fragmentary side elevational view of the antenna assemblyshown in FIGURE 4 with a portion sectioned for clarity of illustration;

FIGURE 6 is a sectional view along the line 66 of FIGURE 5;

FIGURE 7 is a fragmentary rear view of a further embodiment of thepresent invention; and

FIGURE 8 is a fragmentary perspective view of still another embodimentof the present invention wherein a folded dipole antenna configurationis utilized.

It has now been found that the foregoing and related objects can bereadily attained in an antenna assembly including at least one movablecable guide means with a flexible electrical conductor movably disposedwith respect to the cable guide means and at least one fixed point so asto form a configuration of a receiving antenna element. Tuning means areprovided for moving the cable guide means relative to the related fixedpoint so as to change the electrical dimensions of the receiving antennaelement and thus provide adjustment in the size of the antenna elementswhich form the configuration of the antenna array.

More specifically, an antenna is formed by the disposition of flexibleelectrically-conductive wire disposed about pulleys or guides, thepulleys or guides being arranged so that they form a related length ofelectrical conductor into a receiving element of an antenna. The elementof the antenna is increased in size by moving one or more of the pulleysor guides outwardly from a fixed point.

In accordance with a preferred aspect of the invention, the guides orpulleys are so arranged that the conductor, as it is removed from theantenna element formed thereby during contraction of the antennaelement, becomes part of the television lead-in transmission line. Thus,there are no stray ends or tails to cause leakage or alternation of theresonant effect of the antenna. Further, as the desired frequencyincreases, the mass of the antenna decreases, and the elements withinthe antenna retain substantially the same electrical properties,proportionally altered by a reduction in size. Additionally, this designavoids the possibility of re-radiation of signals which could otherwisetend to create undesrable interference images in the received signalpattern (such as ghosts in the picture of a television receiver).

In accordance with still another aspect of the present invention, theantenna may be raised and lowered, or shifted laterally, so as to seekout space loops and to avoid space nodes, whereby the antenna itself isin a pattern of maximum signal strength to take advantage of thegreatest possible electromagnetic field in the immediate area.

Relatively simple mechanical elements may be utilized for adjusting thephysical size of the receiving elements of the antenna and for raisingand lowering the antenna which permits employment of a simpleconfiguration of electrical control and connection for the operation ofmotors which perform these functions. Additionally, a variety ofalternative embodiments may be utilized for the manipulation of the sizeof the antenna elements which enable the choice for antenna assembliesof differing cost, reliability, and performance, as may be required tosuit a variety of needs in the marketplace.

In one form the cable guide means includes two cable guides and thetuning means is adapted to move the cable guides along paths whichdiverge outwardly away from the fixed point and the flexible electricalconductor is disposed about the fixed point and the cable guides so asto define substantially a triangle. Preferably one end of the flexibleconductor is disposed at the fixed point and the conductor follows apath from the fixed point around each of the guides and again past thefixed point so as to form a substantially closed triangular loop. In thepreferred embodiment, a second triangular loop generally similar to thefirst herebefore described is disposed in the same plane and adjacent tothe first loop. The fixed points of the two loops are spaced inproximity to one another so that the triangular loops comprise a doubleelement array with one element being the mirror image of the other. Thelengths of the flexible electrical conductors not included within therelated triangular loops are disposed parallel to each other so as toform a transmission line.

In another embodiment, the cable guide means includes two cable guideseach cooperating with a fixed point with the flexible electricalconductor being disposed relative to the two guides and cooperatingfixed points so as to form a variable length folded dipole. Orientingmeans are additionally included which cooperate with the tuning meansand which are disposed with respect to the two fixed points and theflexible electrical conductor so as to orient differential elements ofthe flexible conductor not included within the dipole in side-by-siderelationship so as to form a transmission line. Most desirably, theorienting means spaces the side-by side conductors of the transmissionline at a distance from one another which provides an impedance in thetransmission line which is substantially equal to the impedance of thefolded dipole.

In accordance with one aspect, the tuning means comprises a base havinga slot therein and a member slidably disposed in the slot which supportsthe guide means. Suitable means drive and selectively position theslidable member at different points along the length of the slot so asto achieve the desired variation in dimension. The drive means maycomprise a reversible motor, gear means driven by the motor, and adriver cooperating with the gear means and which is engaged with theslidable mem ber so that the drive means operates the slidable member inopposite directions within the slot in response to the direction ofrotation of the motor.

Referring now in detail to FIGURE 1, an antenna assembly is shownconnected to the upper end of a regular TV antenna mast 20 which isconnected to the assembly by means of a coupling 22 which may befastened thereto by any suitable means such as the bolt or rivet 24.Affixed to the coupling 22 is a housing 26 containing a gear train, athrust bearing and other suitable apparatus (not shown) to drive theworm gear or lead screw 28 by the motor 30. Rotation of the worm gear orlead screw 28 is confined within an internal contact helical spur gear32 so that, as the worm gear or lead screw 28 rotates, it will cause thehelical spur 32 to advance thereon. The helical spur 32 is aflixed bysuitable fastening means 34 to the inside of a vertically moving mast36, so that advancement of the helical spur 34 will cause a raising orlowering of the vertical moving mast 36.

The vertically movable mast 36 is prevented from rotation due tostresses placed thereon through the action of the helical spur 32 bymeans of an eye bolt 38 which is afiixed to the helical spur 32 andwhich passes through a slot 40a in the fixed mast stub 40, within whichthe vertically movable mast 36 is slidably disposed. The eye ball 38engages a limit switch operating rod 42 which is constrained by a pairof eye bolts 44, 46 rigidly affixed to the fixed mast stub 40.

Upon the limit switch operating rod 42 are fastened an upper limitswitch rod driver 46 and a lower limit switch rod driver 48. When thehelical spur 32 reaches its uppermost operating position relative to thelimit switch operating rod 42, the eye bolt 38 will contact the upperlimit switch rod driver 46 so as to raise the limit switch operating rod42, thereby causing an eyelet 42a at the lower end thereof to operate areversing limit switch 50 by moving its toggle arm 52 from a firstposition to a second position. Similarly, as the helical spur 32 reachesits lower limit of travel, the eye bolt 38 will contact the lower limitswitch rod driver 48 so as to cause the limit switch rod 42 to move thetoggle arm 52 from the second position to the first position (as shownin FIGURE 1). The worm gear or lead screw 28 is supported co'axially bythe upper bearing 54 which permits free rotation thereof Within thevertically movable mast 36.

At the top of the vertically movable mast 36, a pair of U-bolts 56firmly clamp the base member 58 thereto. On the base member 58 is anantenna assembly which includes a motor 60, preferably of the reversingtype, which is connected through a gear train 62 to a drive drum orwinch 64. In driving relationship with the winch 64 is a drive cable 66which passes about the idler pulley 70 and has its opposite ends affixedto a central link 68 which is pulled to the right or left as seen inFIGURE 1 in response to the direction of rotation.

The central link 68 operates an upper link 72 and a lower link 74 whichhave one end pivotably fastened thereto by means of suitable pins orbolts 76. The opposite ends of each of the links 72, 74 are pivotallyconnected to ends of an upper post 80 and a lower post 82, respectively,and are held in place thereon by corresponding spring clip fasteners 84,86.

The posts 80, 82 are slidable in the slots 88, 90- which are formed in abase 92 of the antenna proper, and wobbling is substantially eliminatedby their respective collets or keepers 94, 96 which provide bearingsurfaces and which restrict the longitudinal movement of the posts.Rotatably mounted on the opposite ends of the posts 80, 82 are a pair ofidler pulleys 98, 100 about which a flexible electrical conductor 102extends.

As seen in the embodiment of FIGURE 2, the flexible electrical conductor102 is fixed at one end to the bearing support for the idler pulley 104over which the conductor 102 also extends for movement along its length.This forms a left hand triangle 106 (as seen in FIGURE 2), whichtogether with a similar right hand triangle 108 comprises a bow-tie typeof antenna. The right hand triangle 108 is comprised of similar elements(designated with the reference subscript a) similar tocorrespondinglynumbered elements of the left-hand triangle 106. Theflexible conductors 102, 102a terminate at corresponding terminals 110,112 to which are also attached the two leads of a regular TV lead-inwire 114. As the pulleys 98, 98a, 100, 100a are caused to move outwardlyfrom the guides 104, 10441, the size of the triangles 106, 108 formed bythe flexible conductors 102, 102a is increased, and the length offlexible conductor 102, 102a disposed between the fixed pulleys 104,104a and the terminals 110, 112 is lessened. As the size of thetriangles increases, the tuned frequency of the antenna decreases.

Rotating with the winch 64 is a wrap-up pulley 116 having a cable :118fixed thereto and wrapped thereabout so that, as the winch 64 rotates ineither direction, the wrap-up pulley 116 will take up or releasecorresponding lengths of the cable 18. The cable 118 is fastened bymeans of a spring 120 to a companion cable 122 which is passed about anidler pulley 124 affixed to the bottom of the cable channel guide member126. As may be seen, the other end of the cable 122, in the embodimentsof FIGURES 5 and 6, is fixed to a cable channel so that as the antennaexpands and contracts, the lengths of flexible conductor 102, 102adisposed between the fixed pulleys 104, 104a and the terminals 110, 112are maintained taut by the operation of the wrap-up pulley 116 incombination with the spring 120.

Turning now to FIGURE 3 in detail, the base 92 has affixed thereto thecable channel guide member 126 together with a pair of support legs 128(only one of which is seen in FIGURE 3), an end support 130, and apulley support 132. The legs 128, support 130', and pulley support 132may be aflixed to the cable channel guide memher 126 or formed as anintegral part thereof. The pulley support 132 has a pair of angularly'disposed surfaces 134, 136 on each side thereof which preferably aredefined by angles which divide between the related pulleys or guides 104and 137, or 104a and 13741, the task of changing the course of theflexible conductor 102 or 102a from vertical to some angle abovehorizontal (considering that the base 92 is normally in a verticalplane). In the case where the flexible conductor 102 or 102a forms anincluded angle at the pulley 104 or 104;: of 30 (which ensuressubstantially a 300 ohm impedance for this type of antenna), the surface136 may be at an angle of 35 with respect to the vertical edge of thecable channel guide member 126, and the surface 134 may be at an angleof 70.

A reversing upper limit switch 138 is mounted on the lowermost portionof the pulley support 132 in this embodiment but may be mountedotherwise at the upper limit of travel of the cable channel 140. Forinstance, the upper limit reversing switch 138 may be an integral partof a limit switch structure inserted into a recess provided therefore asillustrated by the dotted lines 142 or the switch 138 may be mounted atthe rear of the pulley support 132, with an actuating means protrudingtherethrough.

The cable channel supports the terminals 110, 122 which join theflexible conductor 102a to the television lead-in wire 114. Aflixed tothe cable channel 140 is the cable 122 which (as illustrated inFIGURE 1) maintains a constant downward tension (as seen in FIG- URE 3)on the flexible conductors 102, 102a without putting undue stress uponthe posts 80, 82, 80a and 82a.

A second embodiment of driving means for the antenna illustrated inFIGURES l-3 is shown in FIGURE 4 with the antenna in its fullycontracted position. The links 68, 68a are driven by a rack and pinion.assembly, rather than by the cable 66 and its associated apparatus asshown in FIGURE 1. In FIGURE 4, the motor and gear train (shown inFIGURE 1) rotate a pinion 152 Which drives the respective links 68, 68ainwardly or outwardly through the racks 154, 154a depending upon whetherthe antenna frequency is to be increased or decreased. The racks 154,154a are suitably restrained by guides 156 and the links 68, 68a may bemounted on the forward and reverse sides, respectively, of thecooperating rack 154, 154a to avoid interference between the variousparts. The pinion 152 also meshes with a spur gear 158 which may drive apotentiometer 160 (shown only schematically in FIGURE 4) to provide anindication of the positional setting of the antenna in a manner similarto the use of a potentiometer to provide an azimuth indication inconjunction with a television antenna rotor.

FIGURE 5 illustrates the antenna assembly shown generally in FIGURE 1with the rack and pinion drive shown in FIGURE 4. Here, the pulley 104has been moved slightly to the left of its natural position so as toillustrate the route of the flexible conductor 102 as it passes over theguides 98 and 100, and the end support 130 and pulley support 132 havebeen omitted for clarity. In addition, the left-hand end (the rear) ofthe post 80 has been broken away for simplicity, and none of the drivinglinks 68, 72, 74 are shown except for the lower end of the link 74 as itis attached to the post 82. It can be seen that the pulley 116 together7 with cables 118 and 122 are utilized to keep a relatively constanttension on the cable channel 140 at various positions of tuning of theantenna. In this embodiment, the spring tensioning means utilizes aspring loaded tension bolt assembly 164.

The cable channel guide member 126 has an additional support 166 with anextension 168 upon which an idler pulley or cable guide 170 is mounted(in the same fashion as the idler pulley or guide 124 is mounted to thecable channel guide member 126). The SuppOrting member 166 may be formedas an integral part of, or affixed to, the rear support member 172 towhich the spring tension assembly 164 is also affixed, and the rearsupport memher 172 is atfixed to the base 92 by the fastener 174. At thebottom of the cable channel guide member 126 is a reversing lower limitswitch 176, mounted so as to be operable by the cable channel 140 as itreaches its lower limit of movement.

As can best be seen in FIGURE 6, the cable channel 140 has across-section of generally lipped C-shaped configuration which permitsit to slide up and down on the cable channel guide member 126, which isof generally T-shaped configuration, without interference from supportmembers 128, 166.

Although the terminals 110, 112 are illustrated as simple bolt and nutassemblies in FIGURES 1 and 2, they preferably are constructed as shownin FIGURE 6, wherein a hole (such as a) is provided for clipping theflexible conductors 102 and 102a so as to completely terminate themwithin the terminals without the necessity of forming loops in the endsthereof, or without leaving tails within them which would causedielectric leakage and loss of signal strength.

In FIGURE 7 there is shown a simplified side elevational view of analternative embodiment similar to the rack and pinion of FIGURE 4 buthaving the advantage of driving parallel to the orientation of the slots88 90. Therein, a worm gear 190 is used to drive a pan of helical spurgears 192, 194. Each of the helical spurs 192, 194 includes a relatedpair of worm gears or lead screws 196, 198 which have threads designedso that, as the spurs 192, 194 rotate, the threads 196 cause a motion tothe left or to the right, respectively, by reason of their engagementwith internal contact helical spur gears 204. The spurs 192, 194 includeslots for keepers or bearings 200 and the lead screws 196, 198 havetheir outer extremities mounted in suitable bearings 206.

As the motor and gear train 60, 62 rotate in one d1rection or the other,the internal contact helical spurs 202, 204 will cause a contraction oran expansion of the antenna elements, which are not shown in FIGURE 7due to the fact that the slots 80, 82 etc. appear beneath the worm gearsor lead screws 196, 198. Since the internal contact helical spurs 202,204 are adequately supported on the lead screws 196, 198, there is nobinding or undue tension placed upon any of the parts of the antennautilizing the arrangement of FIGURE 7. As an alternative, however, foran inexpensive design, the base 92 may be eliminated and a frame may beutilized to support a motor and bearings 202, 204, 206 thus eliminatingthe need for guide slots 80, 82. However, such an arrangement would notbe as durable as an arrangement including both a base 92 with slots 80,82 and the worm drive arrangement shown in FIGURE 7.

There are many possible alternatives in the method of driving the posts80, 82 etc., so as to tune the antenna. In a variation of the cabledrive of FIGURE 1, additional cable guides could be provided at the endsof the slots, and the links 68, 72, 74 etc. eliminated. This has theadvantage that the force exerted on the posts 80, 82 and collets 94, 96is now directly parallel with the orientation of slots 88, 90 so thatthere is no tendency for binding. As another alternative to the driveshown in FIGURE 1, the link 68 may be eliminated and the links 72 and 74pivotably joined together.

For a simple design, a plurality of tension springs could be used tobias the antenna into its fully expanded position. The drive of theantenna would then be accomplished by causing the wrap-up pulley 116(shown in FIGURES l and 5) to draw the antenna into a contractedposition by exerting pressure on the cables 118, 122 so as to utilizethe flexible conductors 102, 102a directly as a driving means forcausing the posts 80, 82 to be drawn along the slots 88, 90. This wouldbe a relatively simple and cheap apparatus, but it has the disadvantageof not being positively driven, which may backlash and additionallywould not operate properly unless the antenna were completely housed ina protective environment as described hereinafter.

FIGURE 8 schematically illustrates an alternative embodiment of theinvention in the form of a folded dipole antenna, wherein a plurality ofpulleys or cable guides 104, 104a, 137, 137a perform functions similarto functions of like-numbered elements in FIGURE 3. The dipole itself isformed about a pair of non-conducting pulleys 114, 146 mounted on posts145, 147 which are adapted for sliding in a pair of related horizontalslots 148, 150. The mechanism for causing the sliding of the postsholding the pulleys 144, 146 may be similar to that shown in FIGURE 1,wherein the cable 66 Would be connected directly to the back of the post145 rather than to the link 68 although other embodiments of the bow-tieantenna drive means described hereinbefore may be adapted for operatingthe dipole antenna illustrated in FIGURE 8. The size of the guides 144,146 is chosen to space the dipole elements less than of a wave lengthapart in accordance with well-known design principles. The drive motors30, 60, and the controls therefor, may be of any suitable type. Onesystem may use well known reversible motors, in which the drive actionmay be selected in either direction of rotation. For use therewith, thelimit reversing switches 50, 138, 176 may be simple, double-pole,double-throw switches which reverse the connection to the motor wheneveroperated.

One of the great advantages of an antenna in accordance with the presentinvention over previous tunable antennae is that the impedance remainssubstantially constant, as does the quality factor (Q) which is theratio between the impedance and the ohmic resistance. This means thatthe senstivity of the antenna, and its attendant ability to discriminatebetween the desired transmitted signal and spurious signals, will remainconstant across the range of tuning capability of the antenna.Additionally, this aspect is further enhanced by the fact that anantenna having a 300 ohm impedance is easily manufactured, permittinguse of regular, inexpensive TV lead-in wire. This impedance can bemaintained at any size due to the fact that elements of flexibleconductor 102, 1020 which are not included within the antenna arrayformed by the cable guides 104 and 98, or 144 are actually formed into atransmission line, which likewise has a 300 ohm impedance. Thus, as theantenna varies in frequency, the electrical characteristics at any givenfrequency remain substantially the same; similarly, there are noadditional adjustments required due to the removal of flexible conductorfrom the antenna array as the size of the antenna is decreased. Thisparticularly important because skin effects and other problems becomemore acute at the higher frequencies which occur when the antenna is atits smallest size.

Another advantage of an antenna in accordance herewith is that the goodproperties of an antenna array are not lost or reduced by space nodes,so that the theoretical advantages of a tuned antenna are made practicalby the elevation adjustment proivded herein. A further advantage of thisinvention is that rather than being an oversized, heavy, complex array,the structure of this invention is small, light and simple. Therectilinear base design permits the structure to be inexpensivelyshielded from weather by a simple plastic housing, or other similarmeans.

Referring again to FIGURE 1, the materials for the base 92 and for theother structural pieces such as the cable channel guide member 126should preferably be made of non-conducting materials such as suitablesynthetic plastics. Since the motor 60 and gear train 62, as well as therack and pinion structures, are mounted close to the antenna, they willhave little effect on the operation thereof. In addition, the drums,cable pulleys or guides, the rack and pinion and the worm drive of FIG-URE 7 may all be made of synthetic plastic. The cable guides 104, 104ashould provide electrical contact with running lengths of conductor 102,102a and the ends of the conductors and, since non-moving guides areself cleaning to ensure good electrical contact, they are preferred.

A typical size of a bow-tie antenna in accordance with this inventionfor UHF channels would include a base which is 25 inches wide and 8inches high, with about 6 /2 inches vertical distance between the outerextremities of the slots 88, 90 and the cable channel guide member 126might be 24 inches long. Since the included angle between the flexibleconductors 102, 102a on each side of the antenna is about 30, theantenna will have substantially a 300 ohm impedance between the flexibleconductors 102, 102a at the terminals 110, 112, so that the assembly mayutilize standard 300 ohm television lead-in wire of the flat variety inwhich the wires are approximately /2 inch apart. Therefore, theterminals 110, 112 and the pulleys 137, 137a should be slightly morethan /2 inch apart to account for the fact that an air dielectric isused between the portions of the flexible conductors 102, 102a that formthe transmission line between the pulleys 137, 137a and the terminals110, 112. In the size illustrated for UHF commercial television, theslots would have an overall length of approximately 9 inches. For VHFrecepition, the overall width of the base 92 would be about 66 inches,the other dimensions being proportional to those described hereinbefore.For the lower VHF channels (2-6), it is possible that the folder dipoleembodiment of FIGURE 8 would be more feasible in terms of overall sizeand weight in view of the environment in which such antenna are to beused. Thus, the folded dipole could be constructed with a lower windresistance, for instance, than the bow-tie antenna.

It should be understood that the detailed hardware illustrated in thevarious figures hereinare illustrative of various means for performingthe expansion and contraction of the antenna as well as raising andlowering it, in accordance with the present invention. However, it canbe seen that the present invention provides a relatively light, small,simple antenna system which has sufiiciently good electricalcharacteristics as to avoid the necessity for multiple arrays andequipmentation. This not only permits a lighter weight antenna, butbecause the antenna may be both tuned and vertically positioned (as wellas rotated) to receive a maximum signal from a particular transmittingstation, it eliminates spurious noise and other interference, andsubstantially prevents out-of-phase reflected signals from causingghosts or images in the television receiver. By raising and lowering theantenna array so as to achieve recepition in a space loop rather than ina space node, the etfectiveness of the tunable antenna array is furtherenhanced. Thus, the signal from the pre ferred antenna assembly of thisdesign maybe properly adjusted in three ways (rotation, elevation, andantenna size) and is not affected by the presence of objects in thearea, indicating that maximum efliciency is being achieved.

Although the invention has been shown and described with respect topreferred embodiments thereof, it should be obvious to those skilled inthe art that the foregoing and other changes and omissions in the formand details thereof may be made therein without departing from thespirit and the scope of the invention, which is to be limited only asset forth in the following claims.

What is claimed is:

1. A receiving antenna assembly comprising a base providing at least oneguide channel; at least two cable guides slidably mounted in saidchannel and cooperating with at least one fixed point therebetween; aflexible electrical conductor movably disposed about said cable guidesand fixed point so as to form the configuration of a receiving antennaelement; and drive means distinct from said flexible conductor formoving said cable guides along paths in generally opposite directions insaid channel so as to change the electrical dimensions of said receivingantenna element and provide a coplanar double loop array, one loop beingsubstantially the mirror image of the other.

2. The antenna assembly of claim 1 wherein said base has a plurality ofslots providing at least one of said channels in which said cable guidesare slidably mounted for movement along said paths.

3. The assembly of claim 1 wherein said base provides at least twochannels which, in turn, provide four paths, a first pair of said pathsdiverging from a first point on said base and a second pair of saidpaths diverging in substantially the same relationship from a secondpoint proximate to said first point; wherein four of said guides areslidably mounted in said channels, a guide being movable by said drivemeans along each of said paths and said drive means simultaneouslymoving all of said guides toward or all away from said points; saidcable being divided into two halves to provide two ends, one of saidends being fixed at said first point with the half of said cableassociated therewith following a path from said first point about thetwo guides movable along said first pair of paths and past said firstpoint, the other of said ends being fixed at said second point with thehalf of said cable associated therewith following a path from saidsecond point about the two guides movable along said second pair ofpaths and past said second point to provide loops adjacently positionedand each in a substantially closed triangular configuration.

4. The antenna assembly of claim 1 including only two of said cableguides, each of said guides cooperating with a fixed point, and whereinsaid flexible electrical conductor is disposed relative to said twoguides and their cooperating fixed points so as to form a variablelength folded dipole.

5. The antenna assembly of claim 1 wherein there are two fixed pointsbetween said guides, and wherein said assembly additionally includesorienting means disposed with respect to the two fixed points and saidflexible electrical conductor so as to orient diiferential elements ofsaid flexible electrical conductor not included within said antennaelement side by side so as to form a transmission line, elements of saidflexible electrical conductor being added to and withdrawn from saidantenna element by being drawn from and added to said transmission linewhereby a substantially constant impedance and quality factor ismaintained in said antenna element as its size is varied.

6. The antenna assembly of claim 5 wherein said orienting means isarranged to space the side by side conductors of said transmission lineat a distance from one another which provides an impedance in saidtransmission line lsubstantially equal to the impedance of said foldedlpO e.

7. The antenna assembly of claim 1 wherein said drive means comprises areversible motor, gear means driven by said motor, and a drivercooperating with said gear means, said driver being engaged to saidguides to move said guides in said channel in response to the directionof rotation of said motor.

8. The antenna assembly of claim 1 wherein said antenna assemblyincludes means for adjusting the position of said receiving antennaelement in a direction selected from vertically and laterally.

9. The assembly of claim 1 wherein said assembly includes a mast havinga fixed portion and a vertically 1 1 1 2 adjustable portion movablysupported relative to said 2,861,268 11/1958 Tinsley 343902 fixedportion; and wherein said adjusting means includes 3,163,863 12/1964Fujino 343823 means to move said movable portion vertically relative tosaid fixed portion. T ER REFERENCES 5 Smallwood: QST, August 1963, pp.4840 References Cited UNITED STATES PATENTS 2,474,242 6/1949 Gieringer343-823 2,702,345 2/1955 Walter 343-823 10 343803, 822, 823

ELI LIEBERMAN, Primary Examiner.

US. Cl. X.R.

